The key answer of exercise 3b

cottage: It's a noun. There are two examples in the text. It's difficult to understand any part of it. stay, one small bedroom, open fire suggest it's some kind of old home, maybe a traditional one.

tough: It's an adjective. There's only one example in the text. It's difficult to understand a part of the word. We could replace tough in it's tough for me to relax with easy or difficult. so I go to the gym (where) I quickly relax tells us that it must mean difficult.